Metal gate field effect transistor (MESFET) device structures are known in the art. These MESFET devices typically include spaced apart source and drain and gate electrodes on a major surface of a semiconductor layer, typically of epitaxial gallium arsenide. The source and drain electrodes make ohmic contact to the semiconductor layer while the gate electrode makes a Schottky barrier contact thereto between the source and drain electrodes, thereby defining a channel region therebetween. The gate electrode is adapted to receive a control signal voltage, in order to modulate the electrical conductance of the channel region and thus control the flow of electrical current between the source and drain electrodes. Such devices are useful as electrical switches and amplifiers.
A problem associated with these MESFET devices in the prior art stems from the source to gate electrode spacing and the gate to drain electrode spacing, as required for electrically insulating the gate electrode from both source and drain electrodes. These spacings give rise to undesirable parasitic series resistances associated with both source to gate and gate to drain paths; thereby both the transconductance and the maximum available output power of the device are degraded, particularly at the high operating frequencies of microwaves (3 to 30 gigahertz).